1. Field of the Invention
The invention relates to the method and system for recovering polluted water, especially for treating ground water and industrial wastewater polluted by organic chlorine compounds.
2. Description of the Prior Art
In case ground water is used as industrial water, etc., it can not be used without being treated if it is polluted. Although there are many causes of polluting ground water, recently pollution of ground water with organic chlorine compounds due to percolation of industrial wastewater into soil is often reported.
As conventional methods for treating organic chlorine compounds e.g. trichloroethylene, tetrachloroethylene and 1,1,1-trichloroethane, contained in ground water, etc., there are evapotranspiration-adsorption process (combination of heated aeration and activated carbon adsorption) and oxidation decomposition process in which potassium permanganate and Fenton's reagent are added into the water. But the most commonly employed method in these days is the evapotranspiration-adsorption process which is a combined method of heated aeration and activated carbon adsorption.
However, in heated aeration and activated carbon adsorption methods, which form the evapotranspiration-adsorption process, activated carbon gets wet due to water vapor generated in the aeration, resulting in considerable capacity reduction of activated carbon for adsorbing organic chlorine compounds. As a result, an amount of the compounds, which are not adsorbed by activated carbon and thus released into the atmosphere, will increase. The released compounds will percolate again into soil. Also, since the saturated activated carbon must be disposed of, an extra cost for disposing the activated carbon is required. In addition, there are other problems including clogging of piping, heat exchanger and diffuser pipe caused by propagation of bacteria in the section where ground water is transferred, heated and aerated. On the other hand, in the oxidation decomposition process using potassium permanganate and Fenton's reagent, etc., consumption of reagent is large, and after-treatment of the treated water is required because the pollutant load is increased due to the use of the reagent and also because heavy metals are contained in the reagent.